The invention relates to a color imaging device comprising an imaging device and a color filter. The color filter has one layer in which at least two systems of filter elements, each passing different colors of light, are formed. The filter elements are formed by coloring with dyes. The invention also relates to a method of manufacturing such a device.
Such a color imaging device is known from U.S. Pat. No. 4,081,277 and is used for recording video images. In this patent, the imaging device is a semiconductor layer which has a system of photosensitive elements. A color filter is provided directly on the system of photosensitive elements. The color filter is one layer having systems of filter elements passing light of various colors, for example red, green and blue. In order to obtain the correct video signal, each filter element of the color filter should be in registration with a photosensitive element of the semiconductor layer.
In manufacturing these filters, a transparent layer is provided on the semiconductor layer, and a barrier layer is then provided on the transparent layer. A pattern of apertures is formed in the barrier layer by means of a photolithographic process. The pattern of apertures corresponds to a system of filter elements of one color to be formed. A dye is then provided in the apertures in the barrier layer, and the regions of the transparent layer underlying the apertures are dyed. After dyeing, the barrier layer is removed. In this manner a first system of filter elements passing, for example red light, is formed. The process is repeated for the formation of the systems of green and blue light-passing filter elements. The color filter may be formed as a stripe filter or as a mosaic filter.
Unfortunately, the manufacture of color filters in the above-described manner gives rise to color defects and errors in the registration of the filter elements with respect to the photosensitive elements. When the transparent layer is dyed via the apertures in the barrier layer, only the regions directly underlying the apertures should be colored. By diffusion in the direction parallel to the layer, however, dye easily travels outside the regions to be colored. As a result of this, regions are formed along the edges of the filter elements in which the colors of the filter elements belonging to different systems run. In addition to the requirement that the transparent layer should have a very small diffusion in the direction parallel to the layer, the layer should of course easily absorb dye. As a result of these two competing requirements the number of suitable materials for the transparent layer is very much restricted.
Furthermore, in order to obtain sharp edges of the apertures in the barrier layer, a barrier layer is required having a large resolving power with respect to the photolithographic process. In addition, three very accurate photolithographic steps are required since the systems of filter elements passing light in different colors must very accurately adjoin each other and the positions of the filter elements of each system should accurately correspond to the associated photosensitive elements.